Efficacy of fungicide treatments for the management of grape powdery mildew in Washington, 2025

Grape powdery mildew, caused by Erysiphe necator, is one of the most common diseases affecting wine grape production globally. Symptoms include white, powdery growth over all green surfaces of the plant, that can inhibit photosynthesis, reduce fruit set, and degrade fruit quality. This report evaluates the efficacy of different fungicide regimes for their ability to control foliar and fruit powdery mildew on Vitis vinifera 'Chardonnay' in Prosser, WA in 2025. Results from this trial can be used to better time different fungicides within a spray regime for improved disease control in wine grapes.